Matroska video format

Eduardo Morras emorrasg at
Wed May 25 07:45:02 UTC 2016

On Tue, 24 May 2016 20:12:23 -0400
Baho Utot <baho-utot at> wrote:

> On 05/24/16 07:32, Eduardo Morras via freebsd-questions wrote:
> > On Sun, 22 May 2016 20:42:41 -0400
> > Baho Utot <baho-utot at> wrote:
> >
> >> I would like to play a Matroskavisoe using vlc, Is this possible?
> > vlc supports mkv container format.
> >
> >> It starts to play but the picture goes in and out of grey
> > It's a video codec problem, not mkv.
> >
> > If it happens once or mixed with other defects, it's (>90%) a tiny
> > corruption on video file.
> >
> > If it happens too often and in the same way (you see 1-2 pictures
> > and goes grey, 1-2 pictures and again grey repeteadly) then the
> > video was codified with a feature vlc can't decode. Upgrade vlc and
> > it's dependence libraries or use other viewer (ffplay from ffmepg)
> > that uses other library (for H264 you have OpenH264, ffmpeg, x264,
> > etc.. and not all of them supports all H264 subformats/modes).
> >
> > If you transcode it with ffmpeg check first ffmpeg/ffplay can play
> > it nicely.
> It does indeed appear as a codec problem, windog 7 will play the
> video just fine.

To know the codec information, use (assuming you have ffmpep installed)

%ffprobe -hide_banner input_file

Input #0, avi, from 'input_file':
    encoder         : VirtualDubMod (build 2540/release)
  Duration: 01:58:56.04, start: 0.000000, bitrate: 1676 kb/s
    Stream #0:0: Video: mpeg4 (Advanced Simple Profile) (XVID / 0x44495658), yuv420p, 704x292 [SAR 1:1 DAR 176:73], 1022 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
    Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 320 kb/s
    Stream #0:2: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 320 kb/s

At Stream #0 you can see video codec (mp4), the profile used (Avanced Simple) and codec implementation (xvid)

These kind of problem occurs when codec use other standard profiles not implemented in decoder or non standard profiles options.

> I tried to transcode it but it did not work

Transcode needs to play it, if the codec library don't support the feature used by creator codec, obtained output file will show the same problems.

Install or reinstall ffmpeg from ports, configure it with SDL support (if not, ffplay is not created) and 

a) #cd /usr/ports/multimedia/ffmpeg
b) #make config
c) Check SDL, x264, if they're not checked
d) UnCheck OpenH264, if it's checked
e) # make install

Use '%ffplay filename' to play the video.

> I am now trying to find out which codec are availiable and if I have 
> them installed.

To show the codecs (decoders) available by your ffmpeg compiled you can use:

%ffmpeg -decoders

and to show everything your compiled ffmpeg can do:

%ffmpeg --help full

adding a new codec needs reconfiguration and recompilation.

P.S. If you config ffmepg port and don't know what were the default ffmpeg port configuration, do '#make rmconfig' to reset it.


---   ---
Eduardo Morras <emorrasg at>

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